The proposed project plans to examine the biobehavioral hypothesis relating chromosome changes to impaired mental functioning in the elderly. Specifically, to determine whether or not hypodiploidy and/or other chromosome changes occur more frequently in glial cells of patients with senile dementia of the Alzheimer type than in those without senile dementia, and to correlate glial cell findings with findings in peripheral lymphocytes. Human brain tissue and blood samples for culturing and chromosome examination will be obtained at autopsy. Sixty subjects, 30 elderly patients 65 years and older with senile dementia and 30 younger patients less that 40 years of age without senile dementia will be evaluated. Comparison between these two groups will maximize the likelihood of detecting chromosome changes and constitutes an important first step in assessing whether or not chromosome change is a biological factor which may underlie senile mental changes. It is only when biological factors which contribute to functional deficits can be identified that the observed functional changes will become more understandable and eventually treatable.